A long time ago in a galaxy far, far away, rumors began circulating about
guild starships in Star Wars:
the Old Republic. These rumors seemed to grow thickest
shortly before the launch of guild vaults, and then the clamor seemed to
die down somewhat. Well, BioWare wasn't quite done with the idea, so
guild-owned capital ships will be added to the game starting in
June.

According to the
announcement, it will be a 3-stage launch: Subscriber Early Access
starting June 24, Preferred Early Access starting on the 29th, and the
"Official Launch" in August.

Key features of the expansion:

Customizable "strongholds," multi-room apartments on multiple planets.
Subscribers will get a free "sky palace" pad on Nar Shaddaa, but each
legacy can own multiple strongholds.

Guild Flagships, essentially flying guild-halls; seems safe to assume
these will also be customizable, but not much information about this
feature is available yet.

Legacy Stronghold Storage - shared storage for all characters on the
same legacy. Way better than inventory management via mail.

The really useful stuff won't be a part of the Early Access period, but
the free Nar Shaddaa sky palace given to subscribers (those who are
subscribed as of May 11) is supposedly valued at 1.5 million credits.
Additional strongholds and unlockable rooms will be available for either
in-game credits or Cartel Coins - expect these features to have a lot of
handy re-directs to the Cartel Market for upgrades and decorations.